Centrum

from WordNet (r) 3.0 (2006)

centrum
    n 1: the main body of a vertebra

from The Collaborative International Dictionary of English v.0.48

Centrum \Cen"trum\, n.; pl. E. {Centrums}, L. {Centra}. [L.,
   center.] (Anat.)
   The body, or axis, of a vertebra. See {Vertebra}.
   [1913 Webster]